Migrate to Wolfi base image and optimize SDK size

- Switch all Dockerfiles from debian:bookworm-slim to svrnty/base-distro:flutter-sdk-latest (Wolfi)
- Use non-root user (UID 65532) instead of custom flutter user
- Strip wrong-platform engine artifacts per variant (web, android, linux)
- Remove dev/, examples/ and compact .git with git gc --prune=all
- Android: multi-stage build for JDK 17 + Android SDK 36 from Debian
- Linux: multi-stage build for clang/cmake/ninja/GTK3 with glibc conflict resolution
- Update Android SDK from 35 to 36 (required by Flutter 3.38.9)

Image sizes: web 1.32 GB, linux 2.43 GB, android 4.22 GB
(down from 4.9 GB, 3.69 GB, 4.15 GB respectively)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Dockerfile

@@ -1,31 +1,29 @@
-FROM debian:bookworm-slim
+FROM svrnty/base-distro:flutter-sdk-latest
 
 ARG FLUTTER_VERSION=3.38.9
 
-LABEL org.opencontainers.image.title="flutter-sdk"
+LABEL org.opencontainers.image.title="flutter-sdk-web"
 LABEL org.opencontainers.image.description="Minimal Flutter SDK for Web/WASM CI builds"
 LABEL org.opencontainers.image.version="${FLUTTER_VERSION}"
 
-# Install minimal dependencies for Flutter web builds
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    git \
-    unzip \
-    xz-utils \
-    ca-certificates \
-    && rm -rf /var/lib/apt/lists/*
+USER 0
 
-ENV FLUTTER_HOME=/opt/flutter
-ENV PATH="${FLUTTER_HOME}/bin:${FLUTTER_HOME}/bin/cache/dart-sdk/bin:${PATH}"
-
-# Download Flutter SDK from official archive
+# Download Flutter SDK and strip unnecessary files in a single layer
 RUN curl -fsSL "https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_${FLUTTER_VERSION}-stable.tar.xz" \
       -o /tmp/flutter.tar.xz && \
     tar xf /tmp/flutter.tar.xz -C /opt && \
-    rm /tmp/flutter.tar.xz
+    rm /tmp/flutter.tar.xz && \
+    rm -rf /opt/flutter/dev \
+           /opt/flutter/examples \
+           /opt/flutter/bin/cache/artifacts/engine/android-* \
+           /opt/flutter/bin/cache/artifacts/engine/linux-* && \
+    chown -R 65532:65532 /opt/flutter
 
-# Mark git directory as safe (tarball is owned by different uid)
-RUN git config --global --add safe.directory "${FLUTTER_HOME}"
+# Mark git directory as safe and compact git history
+RUN git config --global --add safe.directory /opt/flutter && \
+    cd /opt/flutter && git gc --prune=all
+
+USER 65532
 
 # Configure for web-only (disable everything else)
 RUN flutter config --enable-web \
@@ -48,10 +46,4 @@ RUN flutter precache --web \
 # Verify installation
 RUN flutter doctor -v
 
-# Create non-root user for CI builds
-RUN groupadd -r flutter && useradd -r -g flutter -m -d /home/flutter flutter && \
-    chown -R flutter:flutter "${FLUTTER_HOME}" /home/flutter
-
 WORKDIR /app
-RUN chown flutter:flutter /app
-USER flutter